Problems that should be paid attention to when using foliar fertilizer
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First, the choice of leaf fertilizer should be targeted
Crop plants mainly absorb nutrients from the soil, and the content of elements in the soil plays a decisive role in the growth of plants. Therefore, before determining the type of leaf fertilizer, the content of elements in the soil and the acidity and alkalinity of the soil should be determined. Conditionally, the presence of elements in the plant body can be determined, or the type of leaf fertilizer can be determined according to the external characteristics of the deficiency factor. And dosage. It is generally believed that in the case of insufficient application of base fertilizer, foliar fertilizers mainly composed of nitrogen, phosphorus and potassium may be used; when sufficient application of base fertilizer is applied, foliar fertilizers mainly based on trace elements may be selected. For example, the falling bud of cotton buds is related to the lack of boron nutrition. Therefore, it is generally applied 2-3 times in the bud stage, and combined with the application of boron fertilizer, the effect of protecting the buds can be obtained; the cleavage of celery It is also caused by boron deficiency, which can be supplemented by spraying borax or boric acid.
Second, the solubility of leaf fertilizer is better
Since the foliar fertilizer is directly sprayed into a solution, the foliar fertilizer must be soluble in water. Otherwise, the insoluble matter in the foliar fertilizer is sprayed onto the surface of the crop, not only can not be absorbed, and sometimes even damage to the leaves. Therefore, the purity of the fertilizer used for spraying should be higher, and the impurities should be less. Generally, the water insoluble matter in the fertilizer should be no more than 5%.
Third, the acidity of leaf fertilizer should be suitable
Nutrient elements have different states of existence under different acid and alkali conditions. To get the most out of the fertilizer, you must have a suitable range of acidity, generally requiring a pH between 5 and 8. If the PH value is too high or too low, in addition to the absorption of nutrients, it will also harm the plants.
Fourth, the concentration of leaf fertilizer should be appropriate
Since the foliar fertilizer is directly sprayed on the surface of the upper part of the crop, unlike the root fertilization, the buffering effect of the soil is lost. Therefore, we must master the spraying concentration of leaf fertilizer. If the concentration is too low, the amount of nutrients in contact with the crop is small, and the effect is not obvious; if the concentration is too high, the leaf will cause burns. However, the same fertilizer is applied to different crops at different concentrations, depending on the type of crop. For example, urea: the concentration of general crop spraying is 1%-2%; the spraying concentration of crops such as open vegetables, melons and fruits is generally 0.5%-1%, and the concentration of spraying on greenhouse vegetables is 1%-2%; vegetables and fruits in open fields The spraying concentration on the crops should be controlled at 0.2%-0.4%, and the seedling spraying concentration in the seedling nursery period should not be higher than 0.2%. Trace elements can be applied or foliar sprayed, but since some trace elements are easily precipitated in the soil and lose their effectiveness, it is best to use foliar spray in production. The spray concentration is usually from 0.3% to 0.5% aqueous solution. The application concentration of copper and molybdenum should be appropriately reduced.
Five, leaf fertilizer should be used with
The physicochemical properties of fertilizers determine that some nutrients are prone to deterioration, so some foliar fertilizers should be used as needed and cannot be stored for a long time. For example, ferrous sulfate leaf fertilizer, the newly formulated should be light green, no precipitation, if the solution turns auburn or produces a reddish brown precipitate, indicating that low-cost iron has been oxidized into high-priced iron, the effectiveness of fertilizer has been greatly reduced. If the water-alkali or calcium content of the ferrous sulfate solution is too high, the rate of precipitation and oxidation will increase. Therefore, in order to reduce the formation of precipitates and slow down the oxidation rate, 10 ml of mineral acid should be added per 100 liters of water in the preparation of ferrous sulfate solution, or 100-200 ml (about 100-200 g) of vinegar can be added to acidify the water. Then dissolve the ferrous sulfate with water that has been acidified. It is of course also possible to use some organic chelated iron fertilizers such as iron fulvic acid and iron-based polyflavones instead of ferrous sulfate.
Six, the application time of leaf fertilizer should be appropriate
In order to prolong the time when the foliage is wetted by the fertilizer solution, it is beneficial to absorb the elements, and the spraying time of the leaf fertilizer is preferably selected before and after the evening wind. This can delay the air drying speed of the leaf surface droplets, which is beneficial to the penetration of ions into the leaves. Spray evenly so that the front of the blade is wet. In case of heavy rain after spraying foliar fertilizer, it should be sprayed again.
Seven, as an effective measure to adjust the disease of plant deficiency, the application is very extensive. However, in order to maximize the benefits of leaf fertilizer, the most critical fertilizer spraying period should be selected according to the growth of different crops to achieve the best results. The common period of leaf fertilizer is shown in the table.